United States

New generation of micro turbines

A US manufacturer of small wind energy conversion systems, Southwest Windpower, sees great potential in the emerging market for off-grid application of micro turbines. The industry, however, is in dire need of a design and engineering standard, the company says.

In the developed world, the market for small wind energy conversion systems (SWECS) has undergone significant change in recent years. No longer are tiny "wind chargers" or micro turbines used mainly by boat owners for topping up their battery power supplies. These days SWECS are more likely to be part of an off-grid system, providing cheaper supplemental power to a mini photovoltaic plant, according to Southwest Windpower. An Arizona manufacturer of small wind systems, Southwest says about 80% of its micro turbines are today sold for land-based applications.

In a modest wind regime of nine miles an hour, or 4 m/s, SWECS can provide DC power at about $0.17/kWh, according to Southwest. It is retailing its new model, the tiny Air 403, at less than $600, producing 1200 kWh a month. The distinctive fish-shaped Air 403, with a rotor diameter of 46 inches (1.15 metres) and weighing only 13 pounds (6 kg), can be mounted on rooftops, boats and recreational vehicles. The company expects shipments of the Air 403 to reach 15,000 units this year. Sales of the 400 watt SWEC have added up to over 3.2 megawatts to date, with over 8000 units sold since the model's introduction in October of last year. Southwest sold a total of 18,000 of its previous 300 watt unit, the Model 303.

David Calley founded the company in 1981 when he was still in high school. It became more active in 1987 with the production of the 500 W Windseeker. Calley then sold the company in 1990, but saw the deal go bad. "They stole the company," Calley recalls. "The buyer didn't pay us. He just changed the locks on the door and said hire a lawyer." Fortunately for Calley, he did not sell the patents on the Windseeker and so restarted the company from scratch in 1992. He designed the Air model in 1993 and introduced it a year later. The company still makes the Windseeker, which has sold steadily over the past decade. "It's a very old design, but people keep buying it," Calley says. "We would redesign it, but our focus is on the next generation Air turbine."

The company is embarking on a "major" research and development program, including building its own wind tunnel, to develop its Air concept. "As far as I know we'll be the only turbine manufacturer with a wind tunnel," Calley says. The two metre diameter tunnel will be capable of producing 70 mph (31 m/s) winds. "The challenge is in the turbine design. It's much more difficult than it looks. The challenge is to integrate the aesthetics with the function," he explains.

Tunnel testing will be useful in setting up a new certification standard for small turbines, which Calley sees as vital for the small turbine industry. "The current International Electrotechnical Commission certification standard is too weak-dangerously weak," he says. "We tried to strengthen it, but we were not very successful."

Southwest is working with the United States National Renewable Energy Laboratory and Underwriters Laboratory (UL) to get the Air UL-certified to a national standard, the first turbine in the US to seek such a designation. Calley still sees the UL certification standard as inadequate, however. "At this point, our industry is a peculiar curiosity that has absolutely no effect on the world," he says. "One way we can contribute to the industry is to make a standard that is truly rigorous that prevents bad turbines that can damage the whole industry," he continues. "In the 1980s, big wind machines experienced that, and now big machines are much more reliable. The 403 is, I think, the first really reliable micro-turbine."

The 403 is a step up from the original Air model 303, Calley claims, with greater power output and less noise. With the earlier model, according to wind turbine dealer Mick Sagrillo, "marketing was a year and a half in front of engineering." Specifically the 303 had problems with overheating, Calley says, as well as with blade strikes against the tower. "Part of the design challenge is that the turbines are often not professionally installed or sited," he says. "They're often sited badly, with high turbulence levels, which are very harmful to turbines." Still, Calley asserts that the return rate was less than one per thousand units sold. "I'm sure that's the highest reliability achieved by a battery charging turbine," he says. "That's what we were trying to achieve-highest reliability."

Since it began shipping the model 403 in October, Southwest has already made seven or eight thousand. About two-thirds of them have been sold abroad. Calley thinks only about 14% have been sold to people so worried about the Y2K (Year 2000) computer bug they are seeking an emergency power supply, though about a quarter of US sales may be inspired by the bug.

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